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Serious Abrasion on Close Surface of Valve Seat
Description

1.The close surface of the valve seat is worn badly.
Reasons
1.The engine works with heavy load for a long term.
2. The valve clearance is too large.
3. The valve sealing contact band is too wide.
4. The fuel contains too much improper materials, such as sulfur.

Burn on the Valve Seat Close Surface and Its Edge
Description

1. The close surface of the valve seat and its edge are burned.
Reasons
1.The poor sealing of the close surface of the valve seat is the direct reason to cause the burning.
2. The over heat engine make the deformation of the valve.
3. While replacing, the valve is not grinded well to match with valve seat.
4. The valve clearance is too small.
5. The valve spring is not elastic enough.
6. The overmuch carbon deposit make the valve blocked and the deposit on the close surface of the valve seat will also cause the poor sealing of the close surface of the valve seat.

Valve Collar Cracking
Description

1.The valve collar cracks.
Reason
1.This failure is caused by over high thermal stress and mechanical load of the valve. When the engine runs with overload, large fluctuation of load and abnormal burning, the valve will deform. As the valve is seated on its seat, it will cause mechanical overload. Such repeated impact makes the valve collar to crack.